They are all around us, I think it is more a matter of finding a healthy person instead. If you can find someone who is mentally healthy and comfortable with herself, that is a person that is more worthwhile. If you have someone who is all over you all the time, these stupid, codependant relationships form.
There is a book with a really stupid title that gives some exceptionally good advice that I would like to recomend.
Be Your Own Dating Service
You can pick it up on Amazon for about $10.00 on Amazon. Quick read, but makes a crapload of sence.